1. Field of the Invention
The present invention relates to tuning of fiber optic gyroscope modulators and more specifically to tuning out a newly discovered imperfection in an integrated optic modulator.
2. Description of the Prior Art
Many different implementations of Fiber Optic Gyroscopes (FOGs) have been developed using integrated Optic Phase Modulators, typically of lithium niobate or other electro-optic materials. Three recent patents on this subject, assigned to the same assignee as the present invention, are U.S. Pat. Nos. 5,309,220, 5,280,339 and 5,278,631. All of the implementations described to date assume that the integrated optic modulator itself is a perfect device, with only a small shunt capacitance (a few picofarads) to distort the modulating signal. Integrated optic modulators used in FOG applications having a serrodyne feedback require a stable scale factor with flat frequency response. These devices typically have flat frequency responses over very wide bandwidths, far exceeding the requirements of most FOG applications. Analysis of the detected waveforms transmitted from the fiber optic gyro indicates that a very small frequency effect exists in the kilo hertz region, which can affect the scale factor and linearity of a FOG by very small amounts. This very subtle additional distortion is not measurable by normal means and is important only for high accuracy applications. This effect has been isolated to the integrated optic modulator and is not related to the external electronics.